Natural gas or methane often occurs in conjunction with deposits of petroleum. When such gas occurs in quantities which are too small for economical transportation to a point of use, the gas is considered "waste gas" and is disposed of in the most convenient manner. In earlier times the gas was simply vented into the atmosphere. In the present, however, safety regulations generally require the waste gas to be burned or flared to prevent fire and explosion hazards. Ignition of the gas may be hazardous because of the inability of the operator to detect the gas or its rate of escape. Thus, large quantities of the gas may be present, which could ignite explosively.
In oil drilling operations, the natural gas becomes mixed with the packing mud in the drill hole. The mud is passed through a mud-gas separator; and thereafter, the major portion of the mud recirculated to the drill hole while the gas is expelled through a flare pipe. Salt water or brine is often encountered in conjunction with oil deposits, and the water, along with a portion of the mud, is drained into a sludge pit. The flare pipe is often used for draining the water, and commonly extends horizontally from the drilling rig to the sludge pit, usually a distance of several hundred feet. In contrast, flare arrangements in refineries and chemical plants are usually oriented vertically because of space limitations.
Heretofore, methods of igniting the waste gas included shooting flaming arrows, tracer bullets, or signal type flares through the gas emanating from the flare pipe. These practices are unreliable and often dangerous to humans or livestock. Another method of igniting the gas is burning an open container of liquid fuel, such as diesel fuel, near the flare pipe outlet. However, the diesel fuel fire is often extinguished by wind or rain, and reignition of the fuel in the possible presence of the gas is extremely hazardous. In a further flare ignition method, the gas is ignited by an electric spark from an automobile spark coil, electric fence charger, or similar type of transformer. However, the electrode elements, being placed directly in the stream of burning gas, are often burned beyond further use. Additionally, the transformers are often damaged either by the radiant heat of the gas flame or by the flame itself being blown back toward the transformer by wind.
Many arrangements have been devised for the ignition of combustible gases vented through vertical flare stacks. Since the majority of vertical flare stacks are associated with fixed industrial plants, the ignition arrangements are often complex and not suited to periodic dismantling, moving, and reassembly as is often the requirement in oil drilling operations. Further, vertical flare igniters often depend for operation on the convective propogation of the flame front within a vertical tube for the ignition of the waste gas. Such an arrangement would not be suitable to ignite waste gas from a horizontal flare pipe, such horizontal flares positioned generally close to the ground.